U.S. patent application number 13/789884 was filed with the patent office on 2014-02-20 for electronic device including transistor and method of operating the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. The applicant listed for this patent is SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Woo-chul JEON, Jae-joon OH, Ki-yeol PARK, Young-hwan PARK, Jai-kwang SHIN.
Application Number | 20140049296 13/789884 |
Document ID | / |
Family ID | 50099638 |
Filed Date | 2014-02-20 |
United States Patent
Application |
20140049296 |
Kind Code |
A1 |
JEON; Woo-chul ; et
al. |
February 20, 2014 |
ELECTRONIC DEVICE INCLUDING TRANSISTOR AND METHOD OF OPERATING THE
SAME
Abstract
An electronic device may include a first transistor having a
normally-on characteristic; a second transistor connected to the
first transistor and having a normally-off characteristic; a
constant voltage application unit configured to apply a constant
voltage to a gate of the first transistor; and a switching unit
configured to apply a switching signal to the second transistor.
The first transistor may be a high electron mobility transistor
(HEMT). The second transistor may be a field-effect transistor
(FET). The constant voltage application unit may include a diode
connected to the gate of the first transistor; and a constant
current source connected to the diode.
Inventors: |
JEON; Woo-chul; (Daegu,
KR) ; PARK; Ki-yeol; (Suwon-si, KR) ; PARK;
Young-hwan; (Seoul, KR) ; SHIN; Jai-kwang;
(Anyang-si, KR) ; OH; Jae-joon; (Seongnam-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRONICS CO., LTD. |
Suwon-Si |
|
KR |
|
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-Si
KR
|
Family ID: |
50099638 |
Appl. No.: |
13/789884 |
Filed: |
March 8, 2013 |
Current U.S.
Class: |
327/109 |
Current CPC
Class: |
H03K 3/012 20130101;
H03K 17/6871 20130101; H03K 2017/6875 20130101 |
Class at
Publication: |
327/109 |
International
Class: |
H03K 3/012 20060101
H03K003/012 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 2012 |
KR |
10-2012-0089672 |
Claims
1. An electronic device comprising: a first transistor having a
normally-on characteristic; a second transistor connected to the
first transistor, the second transistor having a normally-off
characteristic; a constant voltage application unit configured to
apply a constant voltage to a gate of the first transistor; and a
switching unit configured to apply a switching signal to the second
transistor.
2. The electronic device of claim 1, wherein the first transistor
is a high electron mobility transistor (HEMT).
3. The electronic device of claim 2, wherein the first transistor
is a nitride based HEMT.
4. The electronic device of claim 3, wherein the first transistor
includes a gallium nitride based material.
5. The electronic device of claim 1, wherein the second transistor
is a metal-oxide-semiconductor field-effect transistor
(MOSFET).
6. The electronic device of claim 5, wherein the second transistor
is a silicon (Si) based MOSFET.
7. The electronic device of claim 1, wherein the first transistor
and the second transistor are connected to each other in a cascode
configuration.
8. The electronic device of claim 1, wherein the constant voltage
application unit includes: a constant current source connected to
the gate of the first transistor; and a diode connected between the
constant current source and the gate of the first transistor.
9. The electronic device of claim 8, wherein, an anode of the diode
is connected to the gate of the first transistor, and a cathode of
the diode is connected to a source of the second transistor.
10. The electronic device of claim 8, wherein the diode is a
Schottky diode.
11. The electronic device of claim 8, wherein a semiconductor
material of the diode is the same as a semiconductor material of
the first transistor.
12. The electronic device of claim 8, wherein the diode includes a
gallium nitride based material.
13. The electronic device of claim 8, further comprising: a
substrate, wherein the diode and the first transistor are on the
substrate.
14. The electronic device of claim 13, wherein the first transistor
includes: a first semiconductor layer formed of a first
semiconductor material on the substrate; a second semiconductor
layer on a first region of the first semiconductor layer and formed
of a second semiconductor material that induces a two-dimensional
electron gas (2DEG) in the first semiconductor layer; the gate on
the second semiconductor layer; and a source and a drain at both
sides of the gate, and wherein the diode includes, a third
semiconductor layer on a second region of the first semiconductor
layer and formed of the second semiconductor material; an anode
forming a Schottky contact with the third semiconductor layer; and
a cathode spaced apart from the anode.
15. The electronic device of claim 8, wherein the constant voltage
application unit includes a plurality of diodes, and the plurality
of diodes of the constant voltage application unit are connected
between the constant current source of the constant voltage
application unit and the gate of the first transistor.
16. The electronic device of claim 1, wherein, the electronic
device includes a semiconductor device part and a driving circuit
part, the semiconductor device part includes the first and second
transistors, and the driving circuit part includes the switching
unit and at least a portion of the constant voltage application
unit.
17. The electronic device of claim 16, wherein, the constant
voltage application unit includes a constant current source and a
diode, the constant current source is included in the driving
circuit part, and the diode is included in the semiconductor device
part.
18. The electronic device of claim 16, wherein, the constant
voltage application unit includes a constant current source and a
diode, and the constant current source and the diode are included
in the driving circuit part.
19. A power device including the electronic device of claim 1.
20. An electronic device comprising: a HEMT having a normally-on
characteristic; a FET connected to the HEMT, the FET having a
normally-off characteristic; a diode connected to a gate of the
HEMT; a constant current source connected to the diode; and a
switching unit configured to apply a switching signal to the
FET.
21. The electronic device of claim 20, wherein the HEMT includes a
gallium nitride based material.
22. The electronic device of claim 20, wherein the diode includes a
gallium nitride based material.
23. The electronic device of claim 20, further comprising: a
substrate, wherein the HEMT and the diode are on the substrate.
24. The electronic device of claim 20, wherein the FET is a silicon
(Si) based MOSFET.
25. The electronic device of claim 20, wherein the HEMT and the FET
are connected to each other in a cascode configuration.
26. A method of operating an electronic device including a first
transistor having a normally-on characteristic and a second
transistor connected to the first transistor and having a
normally-off characteristic, the method comprising: applying a
constant voltage to a gate of the first transistor to increase a
voltage between the gate and a source of the first transistor; and
applying a switching signal to the second transistor while the
constant voltage is applied to the gate of the first
transistor.
27. The method of claim 26, wherein the electronic device further
includes, a constant current source connected to the gate of the
first transistor and, a diode connected between the constant
current source and the gate of the first transistor, and the
applying the constant voltage includes applying the constant
voltage to the gate of the first transistor by using the constant
current source and the diode.
28. The method of claim 27, wherein an anode of the diode is
connected to the gate of the first transistor, and a cathode of the
diode is connected to a source of the second transistor.
29. The method of claim 27, wherein the diode is a Schottky
diode.
30. The method of claim 26, wherein the first transistor is a
HEMT.
31. The method of claim 26, wherein the second transistor is a
MOSFET.
32. The method of claim 26, wherein the first transistor and the
second transistor are connected to each other in a cascode
configuration.
33. An electronic device comprising: a first transistor connected
to a second transistor, the first transistor having a normally-on
characteristic, and the second transistor having a normally-off
characteristic; and a driving circuit, the driving circuit being
configured to apply a constant voltage to a gate of the first
transistor, and the driving circuit being configured to apply a
switching signal to a gate of the second transistor.
34. The electronic device of claim 33, wherein the first transistor
is a high electron mobility transistor (HEMT), the second
transistor is a metal-oxide semiconductor field-effect transistor
(MOSFET), and the first transistor and the second transistor are
connected to each other in a cascode configuration.
35. The electronic device of claim 33, wherein the driving circuit
includes a constant current source that is connected to an anode of
a diode and a gate of the first transistor, a cathode of the diode
is connected to a source of the second transistor, and the driving
circuit further includes a switching unit that is connected to a
gate of the second transistor.
36. The electronic device of claim 35, wherein the diode and the
first transistor are on a common substrate.
37. The electronic device of claim 35, wherein the diode is a
Schottky diode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.119
to Korean Patent Application No. 10-2012-0089672, filed on Aug. 16,
2012, in the Korean Intellectual Property Office, the disclosure of
which is incorporated herein in its entirety by reference.
BACKGROUND
[0002] 1. Field
[0003] The present disclosure relates to electronic devices
including transistors and/or methods of operating the electronic
devices.
[0004] 2. Description of the Related Art
[0005] Various power conversion systems include a device for
controlling flow of an electric current through ON/OFF switching
operations such as a power device. In a power conversion system, an
efficiency of the entire system may depend on an efficiency of a
power device.
[0006] Power devices that are currently commercialized are mostly
power metal-oxide-semiconductor field-effect transistors (MOSFETs)
or insulated gate bipolar transistors (IGBTs) which are based on
silicon (Si). However, it is difficult to increase an efficiency of
the power device based on silicon due to limitations in physical
properties of the silicon and in manufacturing processes. To
overcome the above limitations, research for increasing conversion
efficiency by applying group III-V based compound semiconductor to
a power device is being conducted. As a result, high electron
mobility transistors (HEMTs) using a heterojunction structure of
compound semiconductors have drawn attention.
[0007] However, HEMTs generally have normally-on characteristics,
which may increase power consumption and make it difficult to
improve/adjust characteristics of electronic devices to which HEMTs
are applied.
SUMMARY
[0008] Provided are electronic devices having excellent performance
and operating characteristics, the electronic devices including
transistors such as high electron mobility transistors (HEMTs).
[0009] Provided are electronic devices having low on-resistance,
the electronic devices including transistors such as HEMTs.
[0010] Provided are methods of operating the electronic
devices.
[0011] Additional aspects will be set forth in part in the
description which follows and, in part, will be apparent from the
description, or may be learned by practice of example
embodiments.
[0012] According to example embodiments, an electronic device
includes: a first transistor having a normally-on characteristic; a
second transistor connected to the first transistor, the second
transistor having a normally-off characteristic; a constant voltage
application unit configured to apply a constant voltage to a gate
of the first transistor; and a switching unit configured to apply a
switching signal to the second transistor.
[0013] In example embodiments, the first transistor may be a high
electron mobility transistor (HEMT).
[0014] In example embodiments, the first transistor may be a
nitride based HEMT.
[0015] In example embodiments, the nitride may include a gallium
nitride based material.
[0016] In example embodiments, the second transistor may be a
field-effect transistor (FET).
[0017] In example embodiments, the second transistor may be a
metal-oxide-semiconductor field-effect transistor (MOSFET).
[0018] In example embodiments, the second transistor may be a
silicon (Si) based MOSFET.
[0019] In example embodiments, the first transistor and the second
transistor may be connected to each other in a cascode
configuration.
[0020] In example embodiments, the constant voltage application
unit may include: a constant current source connected to the gate
of the first transistor; and a diode connected between the constant
current source and the gate of the first transistor.
[0021] In example embodiments, an anode of the diode may be
connected to the gate of the first transistor, and a cathode of the
diode may be connected to a source of the second transistor.
[0022] In example embodiments, the diode may be a Schottky
diode.
[0023] In example embodiments, the diode may include the same
semiconductor material as the semiconductor material of the first
transistor.
[0024] In example embodiments, the diode may include a gallium
nitride based material.
[0025] In example embodiments, the electronic device may further
include a substrate and diode and the first transistor may be on
the substrate.
[0026] In example embodiments, the first transistor may include: a
first semiconductor layer formed of a first semiconductor material
on the substrate; a second semiconductor layer on a first region of
the first semiconductor layer and formed of a second semiconductor
material that induces a two-dimensional electron gas (2DEG) in the
first semiconductor layer; the gate on the second semiconductor
layer; and a source and a drain at both sides of the gate.
[0027] In example embodiments, the diode may include a third
semiconductor layer on a second region of the first semiconductor
layer and formed of the second semiconductor material; an anode
forming a Schottky contact with the third semiconductor layer; and
a cathode spaced apart from the anode.
[0028] In example embodiments, the constant voltage application
unit may include a plurality of diodes. The plurality of diodes of
the constant voltage application unit may be connected between the
constant current source of the constant voltage application unit
and the gate of the first transistor.
[0029] In example embodiments, the electronic device may include a
semiconductor device part and a driving circuit part.
[0030] In example embodiments, the semiconductor device part may
include the first and second transistors, and the driving circuit
part may include the switching unit and at least a portion of the
constant voltage application unit.
[0031] In example embodiments, the constant voltage application
unit may include a constant current source and a diode and the
constant current source may be included in the driving circuit
part, and the diode may be included in the semiconductor device
part. Alternatively, the constant current source and the diode may
be included in the driving circuit part.
[0032] According to example embodiments, a power device includes
the electronic device.
[0033] According to example embodiments, an electronic device
includes a HEMT having a normally-on characteristic; a FET
connected to the HEMT, the FET having a normally-off
characteristic; a diode connected to a gate of the HEMT; a constant
current source connected to the diode; and a switching unit
configured to apply a switching signal to the FET.
[0034] In example embodiments, the HEMT may include a gallium
nitride based material.
[0035] In example embodiments, the diode may include a gallium
nitride based material.
[0036] In example embodiments, the electronic device may further
include a substrate. The HEMT and the diode may be f on the
substrate.
[0037] In example embodiments, the FET may be a silicon (Si) based
MOSFET.
[0038] In example embodiments, the HEMT and the FET may be
connected to each other in a cascode configuration.
[0039] According to example embodiments, a power device includes
the electronic device.
[0040] According to example embodiments, a method of operating an
electronic device including a first transistor having a normally-on
characteristic and a second transistor connected to the first
transistor and having a normally-off characteristic, the method
including: applying a constant voltage to a gate of the first
transistor so as to increase a voltage between the gate and a
source of the first transistor; and applying a switching signal to
the second transistor while the constant voltage is applied to the
gate of the first transistor.
[0041] In example embodiments, the electronic device may further
include a constant current source connected to the gate of the
first transistor and a diode connected between the constant current
source and the gate of the first transistor. The applying the
constant voltage may include applying the constant voltage to the
gate of the first transistor by using the constant current source
and the diode.
[0042] In example embodiments, the anode of the diode may be
connected to the gate of the first transistor and a cathode of the
diode may be connected to a source of the second transistor.
[0043] In example embodiments, the diode may be a Schottky
diode.
[0044] In example embodiments, the first transistor may be a
HEMT.
[0045] In example embodiments, the second transistor may be a
FET.
[0046] In example embodiments, the second transistor may be a
MOSFET.
[0047] In example embodiments, the first transistor and the second
transistor may be connected to each other in a cascode
configuration.
[0048] According to example embodiments, an electronic device
includes: a first transistor connected to a second transistor, and
a driving circuit. The first transistor has a normally-on
characteristic, and the second transistor has a normally-off
characteristic. The driving circuit is configured to apply a
constant voltage to a gate of the first transistor. The driving
circuit is configured to apply a switching signal to a gate of the
second transistor.
[0049] In example embodiments, the first transistor may be a high
electron mobility transistor (HEMT), the second transistor may be a
metal-oxide semiconductor field-effect transistor (MOSFET), and the
first transistor and the second transistor may be connected to each
other in a cascode configuration.
[0050] In example embodiments, the driving circuit may include a
constant current source that is connected to an anode of a diode
and a gate of the first transistor, a cathode of the diode may be
connected to a source of the second transistor, and the driving
circuit may further include a switching unit that is connected to a
gate of the second transistor.
[0051] In example embodiments, the diode and the first transistor
may be on a common substrate.
[0052] In example embodiments, the diode may be a Schottky
diode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] These and/or other aspects will become apparent and more
readily appreciated from the following description of non-limiting
example embodiments, taken in conjunction with the accompanying
drawings in which:
[0054] FIG. 1 is a circuit diagram of an electronic device
according to example embodiments;
[0055] FIGS. 2A and 2B are circuit diagrams for explaining a method
of operating the electronic device of FIG. 1 according to example
embodiments;
[0056] FIG. 3 is a cross-sectional view of an example stack
structure of a first transistor and a diode of the electronic
device of FIG. 1 according to example embodiments;
[0057] FIG. 4 is a cross-sectional view of an example stack
structure of a first transistor and a diode of the electronic
device of FIG. 1 according to example embodiments;
[0058] FIG. 5 is a circuit diagram of a configuration of a constant
current source of FIG. 1 according to example embodiments; and
[0059] FIG. 6 is a circuit diagram of an electronic device
according to example embodiments.
DETAILED DESCRIPTION
[0060] Various example embodiments will now be described more fully
with reference to the accompanying drawings in which some example
embodiments are shown. Example embodiments, may, however, be
embodied in many different forms and should not be construed as
being limited to the embodiments set forth herein; rather, these
example embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of example
embodiments of inventive concepts to those of ordinary skill in the
art. In the drawings, the thicknesses of layers and regions are
exaggerated for clarity. Like reference numerals in the drawings
denote like elements, and thus their description may be
omitted.
[0061] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another
element, there are no intervening elements present. As used herein
the term "and/or" includes any and all combinations of one or more
of the associated listed items.
[0062] It will be understood that, although the terms "first",
"second", etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. These terms are only used to distinguish one
element, component, region, layer or section from another element,
component, region, layer or section. Thus, a first element,
component, region, layer or section discussed below could be termed
a second element, component, region, layer or section without
departing from the teachings of example embodiments.
[0063] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" other elements or features would
then be oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly.
[0064] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting of example embodiments. As used herein, the singular forms
"a," "an" and "the" are intended to include the plural forms as
well, unless the context clearly indicates otherwise. It will be
further understood that the terms "includes," "including,"
"comprises" and/or "comprising," when used in this specification,
specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0065] Example embodiments are described herein with reference to
cross-sectional illustrations that are schematic illustrations of
some example embodiments and intermediate structures of example
embodiments. As such, variations from the shapes of the
illustrations as a result, for example, of manufacturing techniques
and/or tolerances, are to be expected. Thus, example embodiments
should not be construed as limited to the particular shapes of
regions illustrated herein but are to include deviations in shapes
that result, for example, from manufacturing. For example, an
implanted region illustrated as a rectangle will, typically, have
rounded or curved features and/or a gradient of implant
concentration at its edges rather than a binary change from
implanted to non-implanted region. Likewise, a buried region formed
by implantation may result in some implantation in the region
between the buried region and the surface through which the
implantation takes place. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the actual shape of a region of a device and are not
intended to limit the scope of example embodiments.
[0066] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which example
embodiments belong. It will be further understood that terms, such
as those defined in commonly-used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0067] Example embodiments will now be described more fully with
reference to the accompanying drawings. In the drawings, the same
reference numerals denote the same elements, and the width and
thicknesses of layers and regions may be exaggerated for
clarity.
[0068] FIG. 1 is a circuit diagram of an electronic device 100
according to example embodiments.
[0069] Referring to FIG. 1, the electronic device 100 may include a
first transistor TR1 and a second transistor TR2 connected to the
first transistor TR1. The first transistor TR1 may have a
normally-on characteristic. This may mean that the first transistor
TR1 is a depletion mode (D-mode) transistor. The first transistor
TR1 may be a high electron mobility transistor (HEMT). For example,
the first transistor TR1 may be a nitride based HEMT. Nitride may
be a gallium nitride based material. For example, the first
transistor TR1 may be a GaN based HEMT; however, example
embodiments are not limited thereto. A breakdown voltage Vbd of the
first transistor TR1 may be higher than several hundreds volts V,
for example, higher than about 700 V, and a drain current Ids
thereof may be higher than about 10 A. However, the breakdown
voltage Vbd and the drain current Ids may vary.
[0070] The second transistor TR2 may have a normally-off
characteristic. This may mean that the second transistor TR2 is an
enhancement mode (E-mode) transistor. The second transistor TR2 may
be a field-effect transistor (FET). For example, the second
transistor TR2 may be a metal-oxide-semiconductor FET (MOSFET).
More specifically, the second transistor TR2 may be a silicon (Si)
based power MOSFET. The breakdown voltage Vbd of the second
transistor TR2 may be below about 50 V, for example, between about
20 V and about 30 V, the drain current Ids thereof may be higher
than about 10 A, and an on-resistance Ron thereof may be below
about 10 m.OMEGA.. However, the breakdown voltage Vbd, the drain
current Ids, and the on-resistance Ron may vary.
[0071] The second transistor TR2 having the normally-off
characteristic is connected to the first transistor TR1 having the
normally-on characteristic so that the first transistor TR1 may be
used like a normally-off device. In other words, although the first
transistor TR1 has the normally-on characteristic, a device CD1 in
which the first transistor TR1 and the second transistor TR2 are
connected to each other may have the normally-off characteristic
due to the second transistor TR2. To solve a normally-on problem,
which is a disadvantage of some HEMTs (for example, TR1), the FET
(MOSFET) having the normally-off characteristic (for example, TR2)
may be connected to the HEMT so that the HEMT may be used like a
normally-off device.
[0072] The first transistor TR1 and the second transistor TR2 may
be connected to each other in a cascode configuration. If a source,
a drain, and a gate of the first transistor TR1 denote S1, D1, and
G1, respectively, and a source, a drain, and a gate of the second
transistor TR2 denote S2, D2, and G2, respectively, the drain D2 of
the second transistor TR2 may be connected to the source S1 of the
first transistor TR1. If the first transistor TR1 and the second
transistor TR2 are connected in the cascade configuration, the
device CD1 including the first transistor TR1 and the second
transistor TR2 may be a "cascode device". Hereinafter, the device
CD1 is referred to as a cascade device CD1.
[0073] A device in which the first transistor TR1 and the second
transistor TR2 are connected to each other, e.g., such as the
cascode device CD1, may operate like a single transistor. A source,
a drain, and a gate of the cascode device CD1 may denote S2, D1,
and G2, respectively. For example, the source S2 of the second
transistor TR2, the drain D1 of the first transistor TR1, and the
gate G2 of the second transistor TR2 may be used as the source, the
drain, and the gate of the cascode device CD1, respectively. For
descriptive convenience, the source, the drain, and the gate of the
cascode device CD1 denote S, D, and G, respectively. The source S,
the drain D, and the gate G of the cascade device CD1 may
correspond to the source S2 of the second transistor TR2, the drain
D1 of the first transistor TR1, and the gate G2 of the second
transistor TR2.
[0074] If the second transistor TR2 is turned on, the cascode
device CD1 is regarded as turned on. Because the first transistor
TR1 having the normally-on characteristic, the second transistor
TR2 having the normally-off characteristic determines whether to
turn on or off the cascode device CD1. Thus, a threshold voltage of
the cascode device CD1 may be determined by the second transistor
TR2. In other words, the threshold voltage of the cascode device
CD1 may be identical or quite similar to a threshold voltage of the
second transistor TR2. If the second transistor TR2 is turned on,
and a desired voltage is applied between the drain D1 of the first
transistor TR1 and the source S2 of the second transistor TR2, a
desired or given current may flow from the drain D1 to the source
S2. Another characteristic other than the threshold voltage, for
example a withstand voltage characteristic or a reverse direction
characteristic, may be mainly determined by the first transistor
TR1. If the first transistor TR1 is the HEMT, excellent withstand
voltage characteristic and reverse direction characteristic may be
secured.
[0075] The electronic device 100 may further include a "constant
voltage application unit" that applies a constant voltage to the
gate G1 of the first transistor TR1. The constant voltage
application unit may include, for example, a constant current
source CCS1 and a diode DD1. The constant current source CCS1 may
be connected to the gate G1 of the first transistor TR1, and the
diode DD1 may be connected between the constant current source CCS1
and the gate G1 of the first transistor TR1. The diode DD1 may be
regarded as connected to the gate G1 of the first transistor TR1,
and the constant current source CCS1 may be regarded as connected
between the diode DD1 and the gate G1 of the first transistor TR1.
An anode A1 of the diode DD1 may be connected to the gate G1 of the
first transistor TR1. A cathode C1 of the diode DD1 may be
connected to the source S2 of the second transistor TR2.
[0076] The "constant voltage" may be applied to the gate G1 of the
first transistor TR1 by using the constant current source CCS1 and
the diode DD1. The constant voltage may correspond to a turn-on
voltage of the diode DD1. If a desired constant current is applied
to the diode DD1 by using the constant current source CCS1, the
diode DD1 is turned on and the constant voltage corresponding to
the turn-on voltage of the diode DD1 may be applied to the gate G1
of the first transistor TR1. The turn-on voltage may correspond to
a forward direction voltage drop of the diode DD1, and thus a
constant voltage corresponding to the forward direction voltage
drop may be applied to the gate G1 of the first transistor TR1. The
turn-on voltage (or the forward direction voltage drop) of the
diode DD1 may be, for example, between about 1 V and about 2 V or
between about 1 V and about 1.5 V, so that a voltage (the constant
voltage) between about 1 V and about 2 V or between about 1 V and
about 1.5 V may be constantly applied to the gate G1 of the first
transistor TR1. Thus, a voltage between the gate G1 and the source
S1 of the first transistor TR1, e.g., Vgs, may increase as much as
the constant voltage. As a result, when the cascode device CD1 is
turned on, since the voltage Vgs of the first transistor TR1 is
high, an on-resistance of the first transistor TR1 may be reduced,
and accordingly, performance and operating characteristic of the
cascode device CD1 may be improved.
[0077] If the constant voltage application unit, for example the
constant current source CCS1 and the diode DD1, is not used, when
the cascode device CD1 is turned on, since the voltage Vgs of the
first transistor TR1 has a minus (-) value close to zero volts (0
V), the on-resistance of the first transistor TR1 may increase, and
accordingly, performance and operating characteristics of the
cascade device CD1 may deteriorate.
[0078] The diode DD1 may be, for example, a Schottky diode, e.g.,
such as a Schottky barrier diode (SBD). The diode DD1 may include a
given semiconductor layer and an electrode (an anode) that forms a
Schottky contact with the given semiconductor layer. The given
semiconductor layer of the diode DD1 may include the same material
as a semiconductor material of the first transistor TR1. For
example, the diode DD1 may include a nitride based semiconductor
layer. The nitride may be a gallium nitride based material. The
diode DD1 and the first transistor TR1 may be formed on the same
substrate. For example, the first transistor TR1 may be formed on a
desired substrate, and the diode DD1 may also be formed on the
desired substrate together with the first transistor TR1. The diode
DD1 and the first transistor TR1 may be configured as a single chip
SC1, and an additional process load due to the formation of the
diode DD1 may be reduced. However, the diode DD1 and the first
transistor TR1 may be formed on different substrates.
[0079] The diode DD1 has a small size and a small current necessary
for turning on the diode DD1, which minimally affects power
consumption of an overall device, such as the electronic device
100. In particular, if the diode DD1 is a gallium nitride based
Schottky diode, since the current necessary for turning on the
diode DD1 is below 1 mA, although the current necessary for turning
on the diode DD1 is continuously applied from the constant current
source CCS1, the entire amount of power consumption may hardly be
affected.
[0080] The electronic device 100 may further include a switching
unit SW1 that applies a switching signal to the second transistor
TR2. The switching unit SW1 may be connected to the gate G2 of the
second transistor TR2. The switching unit SW1 may be used to apply
a desired switching signal (for example, a pulse form voltage
signal) to the gate G2 of the second transistor TR2 and turn on (or
turn off) the second transistor TR2. For example, the cascode
device CD1 may be turned on (or turned off) by turning on (or
turning off) the second transistor TR2. The configuration of the
switching unit SW1 is well known, and thus a detailed description
thereof is omitted.
[0081] The electronic device 100 of FIG. 1 may include a
semiconductor device part P10 and a driving circuit part P20 for
driving the semiconductor device part P10. The semiconductor device
part P10 may include the first transistor TR1 and the second
transistor TR2. The semiconductor device part P10 may further
include the diode DD1. The driving circuit part P20 may include the
constant current source CCS1 and the switching unit SW1. However,
according to example embodiments, the diode DD1 may be included in
the driving circuit part P20 rather than the semiconductor device
part P10. When the constant current source CCS1 and the diode DD1
constitute the "constant voltage application unit", a portion
(e.g., the constant current source CCS1) of the constant voltage
application unit may be included in the driving circuit part P20,
and another portion (e.g., the diode DD1) thereof may be included
in the semiconductor device part P10. Alternatively, the entire
constant voltage application unit (e.g., CCS1 and DD1) may be
included in the driving circuit part P20. The driving circuit part
P20 may be a driver integrated circuit (IC).
[0082] FIGS. 2A and 2B are circuit diagrams for explaining a method
of operating the electronic device 100 of FIG. 1 according to
example embodiments.
[0083] Referring to FIG. 2A, a desired constant voltage V1 may be
applied to the gate G1 of the first transistor TR1. The constant
voltage V1 may be applied by using the constant current source CCS1
and the diode DD1. If a desired constant current I1 is applied from
the constant current source CCS1 to the diode DD1, the diode DD1 is
turned on, and thus the constant voltage V1 corresponding to a
turn-on voltage (or a forward direction voltage drop) of the diode
DD1 may be applied to the gate G1 of the first transistor TR1.
[0084] Referring to FIG. 2B, in a state where the constant voltage
V1 is applied to the gate G1 of the first transistor TR1, the
second transistor TR2 may be turned on by using the switching unit
SW1. If a desired voltage is applied between the drain D1 of the
first transistor TR1 and the source S2 of the second transistor
TR2, a desired current I10 may flow from the drain D1 to the source
S2 via the first and second transistors TR1 and TR2. As described
above, if the constant voltage V1 is applied to the gate G1 of the
first transistor TR1, a voltage between the gate G1 and the source
S1 of the first transistor TR1, i.e. the voltage Vgs, may increase
as much as the constant voltage V1, and consequently, an
on-resistance of the first transistor TR1 may be reduced. For
example, the voltage Vgs may increase from a negative (-) value
close to 0V to a positive (+) value between about 1 V and about 2 V
or a range beyond 2 V, so that the on-resistance of the first
transistor TR1 may be reduced. Thus, performance and operating
characteristics a device (i.e. the cascode device CD1 of FIG. 1)
including the first transistor TR1 and the second transistor TR2
may be improved.
[0085] FIG. 3 is a cross-sectional view of an example stack
structure of the first transistor TR1 and the diode DD1 of the
electronic device 100 of FIG. 1 according to example
embodiments.
[0086] Referring to FIG. 3, a first semiconductor layer SL10
including a first semiconductor material may be disposed on a
substrate SUB10. The substrate SUB10 may include, for example,
sapphire, silicon (Si), silicon carbide (SiC), sapphire, or gallium
nitride (GaN). However, example embodiments are not limited
thereto, and the material of the substrate SUB10 may be modified in
various ways. The first semiconductor layer SL10 may include a
group III-V compound semiconductor material (the first
semiconductor material). For example, the first semiconductor layer
SL10 may be a gallium nitride based material layer (for example,
GaN). The first semiconductor layer SL10 may be an undoped GaN
layer, or a GaN layer doped with desired impurities if necessary.
Although not shown, a buffer layer may be further disposed between
the substrate SUB10 and the first semiconductor layer SL10. The
buffer layer reduces (and/or prevents) crystallinity of the first
semiconductor layer SL10 from being deteriorated by reducing a
difference between the substrate SUB10 and the first semiconductor
layer SL10 in terms of a lattice constant and a thermal expansion
coefficient. The buffer layer may have a single-layer or a
multi-layer structure including at least one nitride that includes
at least one of aluminium (Al), gallium (Ga), indium (In), and
boron (B). For example, the buffer layer may have the single-layer
or the mufti-layer structure including at least one of AlN, GaN,
AlGaN, InGaN, AlInN, and AlGaInN.
[0087] A second semiconductor layer SL20 including a second
semiconductor material may be disposed on a first region of the
first semiconductor layer SL10. The second semiconductor layer SL20
may be a material layer that induces a two-dimensional electron gas
(2DEG) in the first semiconductor layer SL10. For example, the
second semiconductor layer SL20 may be formed of a material (the
second semiconductor material) that includes a 2DEG in the first
semiconductor layer SL10. The 2DEG may be formed in the first
semiconductor layer SL10 under an interface between the first
semiconductor layer SL10 and the second semiconductor layer SL20.
The second semiconductor layer SL20 may include a material (the
second semiconductor material) having different polarization
characteristic, energy bandgap and/or lattice constant from those
of the first semiconductor layer SL10. The second semiconductor
layer SL20 may include a material having a polarizability and/or
energy bandgap that is greater than that of the first semiconductor
layer SL10. For example, the second semiconductor layer SL20 may
have a single-layer or a multi-layer structure including at least
one nitride that including at least one of aluminium (Al), gallium
(Ga), indium (In), and boron (B). As a specific example, the second
semiconductor layer SL20 may have the single-layer or the
multi-layer structure including at least one of AlGaN, AlInN,
InGaN, AlN, and AlInGaN. The second semiconductor layer SL20 may be
an undoped layer, or may be a layer doped with desired impurities.
A thickness of the second semiconductor layer SL20 may be less than
several tens of nm. For example, a thickness of the second
semiconductor layer SL20 may be less than about 50 nm.
[0088] A gate electrode G10 may be disposed on the second
semiconductor layer SL20. A source electrode S10 and a drain
electrode D10 spaced apart from the gate electrode G10 may be
provided. The source electrode S10 and the drain electrode D10 may
be electrically connected to the 2DEG. The source electrode S10 may
be closer to the gate electrode G10 than the drain electrode D10.
In other words, a distance between the source electrode S10 and the
gate electrode G10 may be shorter than that between the drain
electrode D10 and the gate electrode G10. However, this is an
example, and the relative distances between the source electrode
S10 and the gate electrode G10 and between the drain electrode D10
and the gate electrode G10 may be different. The source electrode
S10 and the drain electrode D10 may contact the second
semiconductor layer SL20 and may extend onto the first
semiconductor layer SLID. For example, the source electrode S10 and
the drain electrode D10 may contact the second semiconductor layer
SL20 and the first semiconductor layer SL10. Also, the source
electrode S10 and the drain electrode D10 may extend inside the
first semiconductor layer SL10. The source electrode S10 and the
drain electrode D10 may directly contact the 2DEG.
[0089] The first semiconductor layer SL10, the second semiconductor
layer SL20, the gate electrode G10, the source electrode S10, and
the drain electrode D10 may constitute a first transistor TR10. The
first transistor TR10 may correspond to the first transistor TR1 of
FIG. 1.
[0090] A third semiconductor layer SL30 may be disposed on a second
region of the first semiconductor layer SL10. The third
semiconductor layer SL30 may include the same material as that of
the second semiconductor layer SL20. Thus, the 2DEG may be formed
in the first semiconductor layer SL10 contacting the third
semiconductor layer SL30. An anode A10 may contact the third
semiconductor layer SL30. The anode A10 may be on the third
semiconductor layer SL30, and may form a Schottky contact with the
third semiconductor layer SL30. The anode A10 may be formed of the
same material as that of the gate electrode G10. However, the anode
A10 may be formed of a different material from the gate electrode
G10. A cathode C10 may be spaced apart from the anode AI10. The
cathode C10 may contact the third semiconductor layer SL30. The
cathode C10 may contact the third semiconductor layer SL30 while
contacting the first semiconductor layer SL10 under the third
semiconductor layer SL30. The cathode C10 may be formed of the same
material as those of the source electrode S10 and the drain
electrode D10. However, the cathode C10 may be formed of a
different material from the source electrode S10 and the drain
electrode D10.
[0091] The third semiconductor layer SL30, the anode A10, and the
cathode C10 may constitute a diode DD10. The diode DD10 may
correspond to the diode DD1 of FIG. 1. The anode A10 of the diode
DD10 may be connected to the gate electrode G10 of the first
transistor TR10.
[0092] A second transistor TR20 may be provided to be connected to
the first transistor TR10. The second transistor TR20 may be the
second transistor TR2 described with reference to FIG. 1. For
example, the second transistor TR20 may be an enhancement mode
(E-mode) transistor having a normally-off characteristic. The
second transistor TR20 may be a FET, such as a MOSFET. As a
specific example, the second transistor TR20 may be a silicon (Si)
based power MOSFET. The second transistor TR20 may be formed on a
substrate different from the substrate SUB10 and may be connected
to the first transistor TR10 at a packaging step.
[0093] A constant current source CCS10 may be connected to the gate
electrode G10 of the first transistor TR10. The constant current
source CCS10 may be connected to the anode A10 of the diode DD10.
The constant current source CCS10 may correspond to the constant
current source CCS1 of FIG. 1.
[0094] The example stack structure of FIG. 3 may be modified in
various ways. For example, a gate insulation layer may be further
disposed between the gate electrode G10 and the second
semiconductor layer SL20, as shown in FIG. 4.
[0095] Referring to FIG. 4, a first transistor TR10' may further
include a gate insulating layer GI10 disposed between the gate
electrode G10 and the second semiconductor layer SL20. The gate
insulating layer GI10 may include at least one of, for example,
Al.sub.2O.sub.3, SiO.sub.x, Si.sub.xN.sub.y, Sc.sub.2O.sub.3, AlN,
Ga.sub.2O.sub.3, Gd.sub.2O.sub.3, Al.sub.xGa.sub.2(1-x)O.sub.3,
MgO, and a combination thereof. Although not disclosed, as long as
an insulating material is used for a general transistor, the
insulating material may be used as a material for the gate
insulating layer G10. The first transistor TR10' of may be a
metal-insulator-semiconductor (MIS) type HEMT.
[0096] Although a case where the first transistors TR10 and TR10'
and the diode DD10 are disposed on the same substrate SUB10 is
illustrated and described with reference to FIGS. 3 and 4, example
embodiments are not limited thereto. For example, the first
transistors TR10 and TR10' and the diode DD10 may be disposed on
different substrates. However, as shown in FIGS. 3 and 4, if the
first transistors TR10 and TR10' and the diode DD10 are disposed on
the same substrate SUB10, a processing load may be reduced, and
productivity may be improved.
[0097] The configuration of the constant current source CCS1 of
FIG. 1 will be described in more detail below. The configuration of
the constant current source CCS1 of FIG. 1 may be identical or
similar to that of an apparatus used to generate a constant current
in a variety of electronic circuits, e.g., such as a constant
current generator. The constant current source CCS1 may have
various configurations.
[0098] FIG. 5 is a circuit diagram of a configuration of the
constant current source CCS1 of FIG. 1, according to example
embodiments. An example of the configuration of the constant
current source CCS1 and a connection relationship between the
constant current source CCS1 and the first and second transistors
TR1 and TR2 is shown in FIG. 5.
[0099] Referring to FIG. 5, the constant current source CCS1 may
include a voltage generator VG1 and at least one transistor, for
example, two transistors TR3 and TR4. Hereinafter, one of the two
transistors TR3 and TR4 is referred to as the third transistor TR3,
and another is referred to as the fourth transistor TR4. A drain D3
of the third transistor TR3 may be connected to the voltage
generator VG1, and a source S3 of the third transistor TR3 may be
connected to the gate G1 of the first transistor TR1 and the diode
DD1. A gate G3 of the third transistor TR3 may be connected to a
drain D4 of the fourth transistor TR4. A source S4 of the fourth
transistor TR4 may be grounded. The constant current source CCS1
may further include a resistor R1. A first end E1 of the resistor
R1 may be connected to the cathode C1 of the diode DD1. A second
end E2 of the resistor R1 may be grounded. The second end E2 of the
resistor R1 may be connected to the source S2 of the second
transistor TR2. Thus, the cathode C1 of the diode DD1 may be
considered to be connected to the source S2 of the second
transistor TR2 via the resistor R1. A gate G4 of the fourth
transistor TR4 may be connected to the first end E1 of the resistor
R1. A controller CT1 may be connected to the gate G3 of the third
transistor TR3 and the drain D4 of the fourth transistor TR4. The
controller CT1 may adjust a signal (a voltage) applied to the gate
G3 of the third transistor TR3. The controller CT1 may be connected
to the voltage generator VG1.
[0100] By applying a voltage to the drain D3 of the third
transistor TR3 from the voltage generator VG1, a current may be
applied to the diode DD1 via the third transistor TR3. The
controller CT1 may sense a voltage applied to the resistor R1 and
adjust a voltage applied to the gate G3 of the third transistor
TR3. As a result, the current applied to the diode DD1 via the
third transistor TR3 may be maintained constant. For example, a
"constant voltage" may be applied to the diode DD1 via the third
transistor TR3.
[0101] The configuration of the constant current source CCS1 of
FIG. 5 may be modified in various ways.
[0102] The above-described configuration of the electronic device
100 may be modified in various ways. As an example, a plurality of
diodes may be connected to the gate G1 of the first transistor TR1,
as shown in FIG. 6.
[0103] Referring to FIG. 6, an electronic device 100A may include a
plurality of diodes DD1 and DD2 connected to the gate G1 of the
first transistor TR1. The plurality of diodes DD1 and DD2 may be
connected in series to the gate G1. Although a case where the two
diodes DD1 and DD2 are connected to the gate G1 is shown in FIG. 6,
three or more diodes may be used. In example embodiments, a voltage
drop effect of two diodes DD1 and DD2 is twice that of a single
diode being used (FIG. 1), and thus a constant voltage applied to
the gate G1 may increase. Therefore, an on-resistance of the first
transistor TR1 may be further reduced, and performance and
operating characteristic of the electronic device 100A may be
further improved. Except for using two diodes DD1 and DD2, the
configuration of FIG. 6 may be the same as that of FIG. 1.
[0104] Electronic devices according to example embodiments may be
applied to, for example, a power device. Power devices having a
normally-off characteristic, a low on-resistance, and an excellent
operating characteristic may be obtained. However, an application
field of the electronic devices according to example embodiments is
not limited to the power device and may be modified in various
ways.
[0105] It should be understood that the example embodiments
described therein should be considered in a descriptive sense only
and not for purposes of limitation. Descriptions of features or
aspects within each electronic device according to example
embodiments should typically be considered as available for other
similar features or aspects in other electronic devices according
example embodiments. For example, it will be understand by one of
ordinary skill in the art that the "constant voltage application
unit" of FIGS. 1 through 6 may have a configuration other than a
combination of the constant current sources CCS1 and CCS10 and the
diodes DD1, DD2, and DD10. Also, the structures of the first
transistors TR1, TR10, and TR10', the second transistors TR2 and
TR20, and the diodes DD1, DD2, and DD10 and materials thereof may
be modified in various ways. The operating method described with
reference to FIGS. 2A and 2B may also be modified. In addition, it
will be understand by one of ordinary skill in the art that the
idea of example embodiments may be applied to a device other than a
power device.
While some example embodiments have been particularly shown and
described, it will be understood by one of ordinary skill in the
art that various changes in form and details may be made therein
without departing from the spirit and scope of the example
embodiments as defined by the following claims.
* * * * *